1. Field of the Invention
The subject invention relates to honeycomb panels and tables, honeycomb panel and table manufacture, and optical tables including honeycomb structures.
2. Information Disclosure Statement
This information disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes pior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness, and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments subsequent in time or priority.
Utility and advantages of honeycomb structures, panels and tables in various fields of technology are well known, as may, for instance, be seen from U.S. Pat. Nos. 3,606,460, by M. J. Shannon, issued Sept. 20, 1971 and disclosing furniture and table construction with honeycomb panels, 3,754,812, by H. Mohn, issued Aug. 28, 1973 and disclosing optical elements with honeycomb support plate, 3,765,993, by S. L. Raffensparger et al, issued Oct. 16, 1973 and disclosing a layup machine for assembling honeycomb core panels, 4,035,061, issued July 12, 1977 and 4,182,553, issued Jan. 8, 1980, by N. K. Sheridon, disclosing honeycomb display devices, and 4,066,249, by J. G. Huber, issued Jan. 3, 1978 and disclosing a modular vacuum work area with honeycomb core; all being herewith incorporated by reference herein.
Reference may also be had to brochures entitled Mechanical Properties of Hexcel Honeycomb Materials, TSB 120, and The Basics on Bonded Sandwich Construction, TSB 124, by Hexcel Corporation (1982 Revision).
For an extensive tutorial discussion on optical honeycomb tables, reference may be had to the 1983-1984 Catalog by the subject assignee, Newport Corporation, pp. 3 et seq.
In this respect, by way of example and not by way of limitation, among the most sensitive applications to which optical tables are put are those involving interferometry, where tolerable relative displacements of reflective elements are measured in fractions of a micron and allowable table top bending or twisting is typically much less than a second of arc.
Even when requirements are less demanding, it is best to choose a table system that offers that kind of performance, thereby eliminating any likelyhood of table related problems.
The rigidity of a panel or table used in optical research is one of the primary performance features and, for a given panel thickness and skin, depends largely on the shear modulus of the core.
For these and related reasons, honeycomb cores are greatly preferred for very stable panel and table systems.
In the past, granite plates and slabs were frequently used in laser holography and interferometry work. However, while granite offers great stability, the lack of a generally acceptable means of securing components to granite surfaces, as well as the great weight of granite slabs, is increasingly displacing them from laboratories and similar environments.
A major advantage of honeycomb panels or tables is that their top skin or table leaf can be provided with a large number of mounting holes which have a very minor effect on panel or table rigidity and strength. Typically, such mounting holes are present in great number and are tapped, thereby permitting the mounting of optical instruments and other components in a wide variety of desired locations.
In some applications, the drilling and tapping of holes in the panel or table top skin leaves residues in the cells of the honeycomb core. Where the honeycomb cores have to be very thick between top and bottom skins for high rigidity and stability, contaminants in the honeycomb cells are sometimes difficult to remove.
This, then, can cause problems in clean-room,vacuum and other environments where contaminants are able to leave honeycomb cells through apertures in the top skin to an extent producing a noticeable effect in the particular environment.
In this respect, it has been claimed that the use of threaded inserts in lieu of tapped top skin holes avoids the use of oil that could affect delicate optical opponents. Reference may in this respect be had to the brochure entitled Optical Hardware, by Melles Griot (1983), pp. 2 to 6. Among the problems of that approach is, of course, the fact that even a medium sized table of, say, four feet by six feet size, requires over threethousand threaded inserts which have to be individually positioned and attached to the top skin, if mounting holes one inch apart are to be provided in the table top.
Another approach would be to close each tapped mounting hole with a threaded stud, before the honeycomb panel or table is put into service. This, too, would require the use and insertion of thousands of studs in practical applications and, moreover, would, of course, only seal off, but not remove, oil and other drilling and tapping residues from honeycomb cells.